The present invention relates to a valve timing control apparatus for an internal combustion engine which is configured to control an opening and closing timing of an intake valve and an exhaust valve in accordance with a driving state.
There is a valve timing control apparatus of a vane type which is arranged to lock a lock pin for fixing a valve timing, into a lock hole at an intermediate position between a most retard angle and a most advance angle, for improving start-up performance at the start.
In this valve timing control apparatus, when the lock of the lock pin is released, it is preferable to move the lock pin in a rearward direction, not by the hydraulic pressure within the advance angle hydraulic chambers and the retard angle hydraulic chambers, and also without receiving an influence of the hydraulic pressure within the advance angle hydraulic chambers and the retard angle hydraulic chambers.
Accordingly, U.S. Patent Application Publication No. 2011/162601 A1 (corresponding to Japanese Patent Application Publication No. 2010-270746) discloses a valve timing control apparatus arranged to act, through a passage for the lock release only, a hydraulic pressure on an annular end surface which is for receiving the pressure, and which is formed on the outer circumference surface of the lock pin, and thereby to move the lock pin in a rearward direction to release the lock.
The passage for the lock release only is a passage hole which is formed by drilling to penetrate through the vane rotor in the radial direction for the ease of the manufacturing operation. Accordingly, a seal member such as a ball is press-fit in an opening portion of the penetrating passage hole on the outer circumference side to close.